The present study will examine possible age-related cognitive changes in the speech perception abilities of older subjects at several different linguistic levels. These include auditory/phonetic processing in segment identification and discrimination, the processing of dynamic acoustic cues in the perception of vowels, and top-down processes in word recognition. Several different experiments will be conducted within each of these three topic areas. Since hearing sensitivity changes are almost inevitably associated with the age factor, the experimental design will control for hearing loss by (1) including older and younger individuals who demonstrate at least "normal" hearing sensitivity for their age group; (2) including both older and younger individuals who show the same range of hearing loss; and (3) using appropriate statistical methods to control for hearing sensitivity while determining if and age-related effect is present. The basic questions to be addressed include the following: Are there auditory/phonetic memory changes in aging which are separable from hearing sensitivity changes? Are there age-related changes in how individuals phonetically process rapidly changing acoustic information (such as formant frequencies) in order to make vowel identifications? Do older individuals make greater (or lesser) use of top-down information in word recognition than do younger listeners? The results of our experiments will be evaluated in terms of both the relevant aging literature and the relevant theoretical models of speech production and word recognition. These data should allow a more accurate understanding of the aging process, in general, and the types of speech processing difficulties the older individual may face, in particular.